What is the recommended treatment for a complicated urinary tract infection (UTI)?

Treatment of Complicated Urinary Tract Infections

For complicated UTIs, obtain urine culture before starting empiric antibiotics, initiate IV therapy with ceftriaxone 1-2g daily, piperacillin/tazobactam 2.5-4.5g three times daily, or an aminoglycoside, then transition to oral therapy after 48 hours of clinical stability and treat for a total of 7-14 days depending on clinical response. 1

Initial Diagnostic Approach

• Always obtain urine culture and susceptibility testing before initiating antimicrobial therapy due to the wide spectrum of potential organisms and increased likelihood of antimicrobial resistance in complicated UTIs 1
• Common pathogens include E. coli, Proteus spp., Klebsiella spp., Pseudomonas spp., Serratia spp., and Enterococcus spp. 1, 2
• All male UTIs should be classified as complicated UTIs, requiring special consideration due to broader microbial spectrum and higher likelihood of resistance 1

Empiric Antibiotic Selection

First-Line IV Options for Hospitalized or Severe Infections

• Ceftriaxone 1-2g once daily 1
• Piperacillin/tazobactam 2.5-4.5g three times daily 1
• Aminoglycosides (gentamicin 5 mg/kg once daily, amikacin 15 mg/kg once daily) with or without ampicillin, especially when prior fluoroquinolone resistance is present 1, 2

For Multidrug-Resistant Organisms (Reserve for Culture-Confirmed Resistance)

• Carbapenems: imipenem/cilastatin 0.5g three times daily or meropenem 1g three times daily 2
• Newer β-lactam/β-lactamase inhibitor combinations: ceftolozane/tazobactam 1.5g three times daily, ceftazidime/avibactam 2.5g three times daily 2
• Plazomicin 15 mg/kg IV every 12 hours specifically for carbapenem-resistant Enterobacteriaceae, with demonstrated lower mortality (24% vs 50%) and reduced acute kidney injury (16.7% vs 50%) compared to colistin-based regimens 2

Oral Step-Down Therapy (After Clinical Improvement)

• Levofloxacin 500mg once daily - FDA-approved for complicated UTI with 5-day regimen for mild cases (E. coli, Klebsiella, Proteus) or 10-day regimen for moderate cases including Pseudomonas 3
• Trimethoprim-sulfamethoxazole 160/800mg twice daily 1, 2
• Oral cephalosporins: cefpodoxime 200mg twice daily, ceftibuten 400mg once daily, or cefuroxime 500mg twice daily 2

Critical caveat: Only use fluoroquinolones when local resistance rates are <10% AND the patient has no history of fluoroquinolone use in the past 6 months 1, 2

Treatment Duration

• Standard duration: 14 days for most complicated UTIs 1, 2
• 7 days for catheter-associated UTIs with prompt symptom resolution 1, 2
• 10-14 days for catheter-associated UTIs with delayed response 1, 2
• 5-day regimen of levofloxacin 750mg once daily may be considered for mild complicated UTI in patients who are not severely ill 1, 3
• Always treat males for 14 days when prostatitis cannot be excluded 1, 2

Transition to Oral Therapy

• Switch to oral therapy when the patient is hemodynamically stable and has been afebrile for at least 48 hours 1, 2
• Reassess after 48-72 hours of empiric therapy to evaluate clinical response 1
• Adjust therapy based on culture and susceptibility results 1

Special Considerations for Catheter-Associated UTIs

• Replace the catheter if it has been in place for ≥2 weeks at onset of infection and is still indicated to hasten symptom resolution and reduce recurrence risk 1, 2
• Remove the urinary catheter as soon as clinically appropriate 1
• A 3-day antimicrobial regimen may be considered for women aged ≤65 years who develop catheter-associated UTI without upper urinary tract symptoms after an indwelling catheter has been removed 1

Critical Pitfalls to Avoid

• Never use moxifloxacin for UTI treatment due to uncertainty regarding effective urinary concentrations 1, 2
• Avoid fluoroquinolones as empiric therapy if local resistance rates exceed 10% or if the patient has used fluoroquinolones in the past 6 months 1, 2
• Do not use shorter treatment courses (<14 days) in males unless prostatitis has been definitively excluded 1, 2
• Avoid treating asymptomatic bacteriuria in non-pregnant patients 1, 2
• Avoid carbapenems and novel broad-spectrum antimicrobials unless culture results indicate multidrug-resistant organisms 1, 2
• Failing to replace long-term catheters at treatment initiation reduces treatment efficacy 2

Monitoring and Follow-Up

• If no clinical improvement with defervescence by 72 hours, reassess and consider extended treatment with urologic evaluation 1, 2
• Obtain follow-up urine culture after completion of therapy to ensure resolution of infection 2
• Complete the full course even after symptom resolution to prevent relapse 1